1. Technical Field
The present invention relates to a physical quantity measuring apparatus (for example, an oscillatory gyroscope that detects an angular velocity by detecting a Coriolis force with respect to the oscillation motion of an oscillator), and an electronic device.
2. Related Art
An example of the configuration of the oscillatory gyroscope is described, for example, in JP-A-2002-174520. According to this reference, an AGC circuit (Automatic Gain Control circuit) configured to maintain the amplitude of the drive oscillations constant is provided in an oscillation drive circuit that excites drive oscillations of the oscillator.
The oscillatory gyroscope (hereinafter, referred to also as the gyroscope) of the cited reference is configured to maintain the drive amplitude constant by the AGC circuit as described above. However, in a state where the amplitude has not been maintained constant by the AGC circuit, the detection sensitivity is non-constant. At the start of oscillation, in particular, the sensitivity varies gradually because the amplitude increases gradually. Such being the case, the gyroscope in the related art has no choice but to render detection signals obtained in the oscillation start period invalid, which extends a start-up time until the desired detection sensitivity is achieved.
In addition, the amplitude of the drive oscillation varies with various disturbances (for example, a fluctuation of the power supply voltage or an impact given to the gyroscope from the outside). Accordingly, even when the AGC circuit is provided, the amplitude of the drive oscillation is kept disturbed over a period until the amplitude that was varied by a disturbance converges to a desired level. The detection sensitivity therefore varies in this period.
For example, in a case where the gyroscope is used to correct camera shaking, the amplitude of the drive oscillation varies with a slightest impact given to the camera. Hence, in order to achieve a gyroscope at a higher degree of accuracy, it is necessary to take a countermeasure against the cause of a mechanical disturbance (impacts and shaking given to an electronic device), not to mention a countermeasure against the cause of an electrical disturbance, such as a fluctuation of the power supply voltage. The problems discussed above, however, cannot be solved by the related art.